SUMMARY/ABSTRACT Amyotrophic lateral sclerosis (ALS) is the most common form of motor neuron disorder that causes muscle weakness, disability, and eventually death. ALS is caused by selective cell death of vulnerable upper and lower motor neurons. Genetic analyses in familial ALS patients have identified several genes with mutations linked to ALS, such as C9ORF72, TDP-43, and SOD1. However, it remains unclear how these mutations lead to selective cell death of motor neurons in ALS patients, and which cell death pathways are responsible for the motor neuron cell death. Early studies suggested the involvement of apoptosis, but a more recent investigation found a role for necroptosis in one cell model. It is plausible that multiple cell death pathways are activated in the course of the disease. We recently reported that inhibition of glutathione peroxidase 4 (GPX4), and subsequent accumulation of lipid peroxides, triggers a unique form of regulated cell death termed ferroptosis. Intriguingly, data from multiple ALS models as well as our own results have suggested that ferroptosis may contribute to the motor neuron cell death in ALS. Based on the experimental results indicating the role of both apoptotic and non-apoptotic cell death pathways in ALS, I propose to test the hypothesis that multiple cell death pathways are activated in ALS motor neurons, focusing on the involvement of ferroptosis. Our long-term goal is to elucidate how cell death pathways are regulated (and deregulated) in human disease, and to contribute to the development of treatment strategies by modulating cell death pathways. We are particularly interested in understanding the ferroptotic cell death pathway. The objective of this proposal is to determine cell death pathways activated in degenerating motor neurons in amyotrophic lateral sclerosis (ALS) focused on the involvement of ferroptosis. Based on the preliminary data, the project will be pursued in two specific aims. In Aim 1, we will identify the specific cell death pathways involved in ALS using motor neuron lines (iPS-MNs) in vitro and using a transgenic mouse model of ALS in vivo. In Aim 2, we will determine the efficacy of ferroptosis inhibitor in ALS iPS-MN cell lines and in SOD1-G93A transgenic mice either as a single-agent or as a combination therapy with suppressors of other cell death modalities. This research will shed light on the molecular mechanism of motor neuron degeneration in ALS, as well as the role of ferroptosis in the disease. It may also lead to the development of new therapeutic strategies. In addition, this SCORE-2 award will enhance the research environment at St. John's University and provide numerous opportunities for motivated students from diverse origin to learn the fundamentals of biomedical research.